Increasing concerns regarding pollution or contamination of water supplies and, in some instance, concerns regarding the effect of chemicals used in the treatment of public water supplies, has led to an increasing demand for household water purification systems. While distillation of water by heating it until it vaporizes, and then condensing the vapor and collecting the condensate is a well known technique for the purification of water, there has been a delay in the development of distillation systems suitable for home use and capable of unattended operation over several distillation cycles.
While batch distillation systems are widely used in various industrial applications, as exemplified by U.S. Pat. Nos. 4,401,512 and 3,364,371, these systems are not readily adaptable for domestic use. Distillation systems for home use are known as exemplified by U.S. Pat. Nos. 4,260,459 to Kirschman and 4,622,102 to Diebel. However, the Kirschmann device, while capable of batch operation, is not capable of continuous operation over several batches. It must be manually operated to fill the system with each batch of water. Furthermore, a valve for venting contaminants which vaporize below the boiling point of pure water must be manually opened and closed during distillation of each batch. The Diebel device, while fully automatic, is not readily adaptable for draining and flushing residue from the boiler as soon as the water therein recedes to a predetermined level.
Fitch U.S. Pat. No. 3,696,003 discloses a laboratory apparatus with means for cleaning the boiler by introducing a cleaning liquid which is distilled. The Fitch device maintains a constant water level in the boiler hence, before cleaning, the boiler must be emptied thereby wasting not only the water therein but also the energy used to heat it. Furthermore, the boiler emptying operation must be manually initiated.